The present invention relates to a color electrostatic recording apparatus for having a color picture recorded by overlapping different color images successively on a single recording medium.
FIG. 6 is a schematic view showing the arrangement of a prior art color electrostatic recording apparatus in which: represented by 51 is a recording medium; 52 and 53 are respectively a winder and a rewinder for feed-in and -out of a web of electrostatic recording paper for the forward and backward movement; 55 is a multi-pin electrode recording head; 54 is a hold-down roller for keeping the recording medium in contact with the multi-pin electrode recording head; 56 is a static eliminator bar; 57, 58, 59 and 60 are developing devices for supplying with developer materials of their respective colors; 61 is a squeeze for recovering used developer materials; 62 and 63 are a press roller and a drive roller respectively for actuating the recording medium to travel forward and backward; and 64 is a reversible driver source.
The operation in this arrangement will be described. The recording medium 51 is transferred in a direction represented by the arrow A by the drive roller 62. During the transfer, an electrostatic latent image of black picture is produced on an effective screen area of the recording medium 51 by the multi-pin electrode recording head 55 and developed with a black color developer material through electrostatic attraction by the developing device 57. The black color developer material applied is then fused while the remaining of developer material is dislocated for recovery. The recording medium 51 bearing the black color image is wound onto the winder 53 and after the recording of information of the black color image is completed, reversely transferred by the driver source 64 for rewinding onto the rewinder 52. After the rewinding, similar images of second, third, and fourth colors e.g. of cyan, magenta, and yellow respectively are then overlaid one another on the black color image in the above described manner to have a picture of four colors (black, cyan, magenta, and yellow).
However, if changes in both the atmospheric humidity and temperature cause the recording medium to expand and/or contract after the electrostatic development in the first color is completed, the corresponding minimum pitch in the recorded image to the electrode minimum pitch of the multi-pin electrode recording head varies for increase or decrease. This allows no accurate overlapping and results in misconvergence of the colors, which will be regarded as a disadvantage of the prior art arrangement.